The present invention relates generally to hermetic refrigeration compressors and especially low capacity refrigeration compressors used in household appliances. More particularly, the invention relates to thrust bearing assemblies for supporting vertical rotor and crankshaft combinations commonly associated with refrigeration compressors. An area of concern long associated with such compressors, as well as other machines, is the amount of mechanical friction that occurs within the compressor during operation. Compressor efficiency is quantified as an energy efficiency ratio (EER), which is derived by dividing the compressor output in BTU/hour by the power consumed by the compressor under standard operating conditions. According to this relationship, it becomes apparent that one way of increasing the efficiency of a compressor is to decrease the amount of power consumed by the compressor without adversely affecting its BTU output.
One source of power consumption within the compressor is the mechanical friction between the bearing frame hub and the rotating rotor and crankshaft combination. Many types of thrust bearings have been used to diminish mechanical friction and thereby reduce the power consumed by a compressor. Thrust bearings of the past have been machined steel, plain or oil film type, multi-layered, a composite of materials, or a ball bearing assembly to name a few. Problems associated with prior art thrust bearings include the following: warpage of copper and copper alloy bearings; expense associated with metallic, alloy materials, multi-layered bearings, and ball bearing assemblies; and complexities in manufacturing associated with ball bearing assemblies.
In particular, ball bearing type thrust bearings employ a pair of flat thrust washers which serve as races between which balls are mounted in a plastic cage. In general, ball type bearings require a lower starting torque than the fluid film type bearings. However, once running under hydrodynamic film, the fluid film type bearings exhibit friction characteristics comparable to those of ball type bearings.
One of the disadvantages of the ball type bearing is the necessity to use through-hardened acid-corrosion resistant metal for the rolling elements and flat thrust washers. The plastic material used for fabricating the bearings cage is sensitive to temperature and has a lower continuous service temperature than the metal balls and thrust washers.
Another disadvantage is the requirement for multiple parts (balls, cage, bearing, and two washers) which increases production costs and results in additional frictional pairs. In addition, ball type bearings produce greater noise than fluid film type bearings.